1. Field of the Invention
The present invention pertains to a multilayer thermoplastic stretch wrap film, particularly a polyolefin stretch wrap film having a cling layer with a thin non-expandable film of slip agent(s) on the outer surface of this layer, in particular of slip agent(s) of limited compatibility with a polymer composition of the cling layer, a method of preparation thereof and the use of the multilayer stretch wrap film according to the invention for stretch wrapping operations of articles or a group of articles.
2. Description of the Related Art
Stretch films that self-seal when portions are overlapped are known as “cling” films. These films are most often multilayer films and are used in applications where it is desirable to securely hold and/or wrap an article or a group of articles, such as load palletization. For load palletization operations, the film is stretched tightly around the good or plurality of articles situated on a pallet, and self-sealed while the film is still in the stretched condition to create a secure, unitised package. Both unstretched or pre-stretched films are used for load palletization and retention of substantial cling properties and good tear properties while the film is stretch-wrapped is required to maintain the integrity of the unitised load.
From WO 95/15851 a multilayer thermoplastic stretch wrap film is known having at least a layer comprising a film forming branched ethylene polymer composition having a density of 0.90 g/cm3 or less and a layer of at least a film forming olefin polymer composition having a density of greater than 0.90 g/cm3. The film may contain a third core layer of an ethylene polymer between the cling layer and the slip layer.
WO 96/29203 discloses a multilayer stretch wrap plastic film having a cling layer comprising ultra low density polyethylene (ULDPE) and a slip layer comprising a low density (high pressure) polyethylene (LDPE) and a solid particulate antiblock agent.
From EP-A-1 022 131 a multilayer blown stretch film is known comprising a first layer having cling properties and comprising a copolymer of ethylene and a C4-C8-α-olefin, the copolymer having a density in the range of 0.85 to 0.89 g/cm3 and a second layer having substantially no cling properties and comprising at least 70 weight percent of a long chain branched low density polyethylene having a density in the range of 0.915 to 0.940 g/cm3. The film is essentially free of cling or anti-cling additives and a core layer may be present between the first and the second layer.
It is the object of the present invention to provide a multilayer thermoplastic stretch film comprising at least a cling layer and a slip layer having a good balance of the desired mechanical properties, exhibiting an improved low noise level during unwinding from a supplier roll and wrapping goods but having also sufficient cling properties to be useful for wrapping.